Roman.java

class Roman{
	public static String getRomanNumeral(int arabicNumber){

		if(arabicNumber>0&&arabicNumber< 4000){

			final LinkedHashMap<Integer, String> numberLimits=
					new LinkedHashMap<>();

			numberLimits.put(1,"I");
			numberLimits.put(4,"IV");
			numberLimits.put(5,"V");
			numberLimits.put(9,"IX");
			numberLimits.put(10,"X");
			numberLimits.put(40,"XL");
			numberLimits.put(50,"L");
			numberLimits.put(90,"XC");
			numberLimits.put(100,"C");
			numberLimits.put(400,"CD");
			numberLimits.put(500,"D");
			numberLimits.put(900,"CM");
			numberLimits.put(1000,"M");

			String romanNumeral="";

			while(arabicNumber>0){
				int highestFound=0;
				for(Map.Entry<Integer, String> current:numberLimits.entrySet()){
					if(current.getKey()<=arabicNumber){
						highestFound=current.getKey();
					}
				}
				romanNumeral+=numberLimits.get(highestFound);
				arabicNumber-=highestFound;
			}

			return romanNumeral;

		}else{
			throw new UnsupportedOperationException(arabicNumber
					+" is not a valid Roman numeral.");
		}
	}
}